1. Field
This disclosure relates to data storage systems. More particularly, the disclosure relates to systems and methods for monitoring data retention in solid-state drives.
2. Description of Related Art
Certain solid-state memory devices, such as flash drives, store information in an array of memory cells constructed with floating gate transistors. In single-level cell (SLC) flash devices, each cell stores a single bit of information. In multi-level cell (MLC) devices, each cell stores two or more bits of information. When a read operation is performed, the electrical charge levels of the cells are compared to one or more voltage reference values (also called “voltage read level” or “voltage threshold”) to determine the state of individual cells. In SLC devices, a cell can be read using a single voltage reference value. In MLC devices, a cell is read using multiple voltage references values. Certain solid-state devices allow for a memory controller to set voltage read levels.
Various factors can contribute to data read errors in solid-state memory devices. These factors include charge loss or leakage over time, and device wear caused by usage. When the number of bit errors on a read operation exceeds the ECC (error correction code) correction capability of the storage subsystem, the read operation fails. Voltage read levels can contribute to a device's ability to decode data.